In recent years there has been an increasing need for composite materials having high fracture toughness, hardness and wear resistance for use in cutting tools, wear parts, and structural applications such as dies, turbines, nozzles, and the like. Due to their high modulus of elasticity, high hardness, high strength, and resistance to chemical reaction with the composite matrix, coated single crystal whiskers of such materials as carbides, nitrides, or carbonitrides of Ti, Zr, Hf, V, Nb, Ta or W could present attractive materials for composite technology. Whiskers of metal carbides or nitrides, for example, titanium carbide, are known. Laboratory methods for their production involve placing a substrate material suitable for whisker growth, for example a graphite or mullite plate or tube, at the center of a quartz tube, and heating the substrate to a temperature suitable for whisker growth. Typical temperatures in such reactors range from about 800.degree.-1400.degree. C. The reactor tube is flushed with hydrogen, and reactant gases, typically in a molar ratio of carbon or nitrogen to metal of about 1:1, are flowed through the heated reactor to form whiskers on the substrate.
Ceramic whiskers coated with MgO are disclosed in U.S. Pat. No. 4,569,886 to Divecha et al. Carbon fibers coated with Si.sub.3 N.sub.4 are disclosed in U.S. Pat. No. 4,214,037 to Galasso et al. However, neither patent discloses the coated metal carbide, nitride, or carbonitride whiskers, or the processes for their production, of the present invention.